Boron penetration and thermal instability of p+ polycrystalline-Si/ZrO2/SiO2/n-Si metal-oxide-semiconductor structures

We report boron penetration and thermal instability of p(+) polycrystalline-Si (poly-Si)/ZrO2 (100 Angstrom)/SiO2 (similar to7 Angstrom)/n-Si metal-oxide-semiconductor (MOS) structures. The flatband voltage shift (DeltaV(FB)) of the p(+) poly-Si/ZrO2/SiO2/n-Si MOS capacitor as determined by capacitance-voltage measurement was similar to0.18 V, corresponding to a p-type dopant level of 1.1x10(12) B ions/cm(2) as the activation temperature increased from 800 to 850 degreesC. Additional DeltaV(FB) of similar to0.24 V was measured after the anneal from 850 to 900 degreesC. Noticeable boron penetration into the n-type Si channel as observed by secondary ion mass spectroscopy also confirmed the V-FB instability with activation annealing above 850 degreesC. An abnormal decrease of accumulation capacitance was also found after anneal at 900 degreesC due to an excessive leakage current which was attributed to the formation of ZrSix nodules at the poly-Si/ZrO2 interface. We observed 4-5 orders of magnitude lower leakage current from the small-size capacitors (<50x50 <mu>m(2)) up to the activation anneal of 850 degreesC for 30 min, while the formation of interfacial ZrSix nodules at 900 degreesC cannot be avoidable even at 0.6-mum-wide gate lines. (C) 2002 American Institute of Physics.